Graduate Thesis Or Dissertation
 

Agroforestry farming in American Samoa : a classification and assessment

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  • Agroforestry is a traditional farming practice in American Samoa that has helped to sustain the livelihood of the native population for centuries. These once self-sufficient islands have become economically dependent on U.S monies and other external resources during the past century. Dependency has caused a shift in the carrying capacity of the islands and has changed cultural attitudes regarding land use. This attitude is expressed on the landscape of changing agricultural and communal lands. Preserving traditional agroforestry practices and improving these systems may be important factors contributing to the future ecological, economic, and cultural sustainability of the territory. The goal of this study was to document and describe agroforestry farming in American Samoa in order to provide base-line information regarding the utilization of agroforestry species, agroforestry farming incentives and constraints, and current practices and systems. Thirty-eight farmers were randomly selected and farmer interviews and field surveys were conducted between the months of May-August 2003. Formal survey questions for the interview were divided into five major sections: woody species usage, livestock, inputs and soil, land tenure, and farmer demographics. Site selection corresponded with the participant farmers. Basic topographical information was collected for each site. Agroforestry practices mentioned during the interview process that were observed on site were documented. Each agroforestry site was placed into an initial classification type based on a visual assessment of plot size, species diversity, and vertical vegetative structure. Subplot data regarding species composition and vertical canopy structure was measured for each site. Data collection was divided into five vertical layers primarily by height: 1) low crop (<1.5m), 2) shrub/sapling (1.5-4m), 3) small tree (4-l0m), 4) large tree (10+m) and 5) climbing vines. For each subplot all ethnobotanically useful plant species were identified. Percent cover of useful species in each stratum layer was estimated and assigned one of seven percent cover classes. Subplot cover classes were averaged to obtain a single site estimate for each species in each stratum. Results from the farmer interviews suggest that agroforestry systems continue to be an important cultural and product resource in American Samoa. Although there is no longer the same level of dependency on these systems for meeting basic needs, agroforestry products continue to supplement household diets and are utilized for a variety of non-timber forest products and ecological services. Several agroforestry practices were observed among the farms in the study. However, the effectiveness of some of the practices including windbreaks, fallow, and erosion control was not optimal. This indicated that farmers could greatly benefit from institutionalized agroforestry practices such as appropriate spacing for wind filtration, improved fallow, and contour farming. Incentives and constraints for practicing agroforestry farming were identified. Some incentives included product variety, tradition, and a growing need for land-use efficiency. Identified constraints included time investment for production and poor labor resources, decreased profit when compared to mono-cultural farming, and the lack of planning prior to agroforestry implementation. The communal land tenure system acted as both an incentive and a disincentive for practicing agroforestry. The initial classification of agroforestry systems included home tree gardens, mixed crop plantations, transitional systems, and open canopy with dispersed tree systems. Agroforestry systems existed along an ecological complexity continuum, where complexity was measured by species diversity and vertical structure. A quantitative assessment of species composition and structure was used as a more objective approach to classifying local agroforestry systems. Non-metric multidimensional scaling was used to ordinate sites along a gradient based on species composition and structure. Several environmental and socio-economic variables were investigated to determine whether any of them demonstrated relationships with vegetative patterns. Species diversity, average number of canopy stratum layers, and elevation were three variables correlated with vegetative patterns. Sites that had high species diversity and were multi-structured were placed at the upper end of the gradient, while sites that had lower diversity with simple structure were generally placed at the lower end of the gradient. This supported the ecological complexity continuum. Less complex sites were associated with high elevations indicating that systems on the heavily populated lowland regions were more species rich and structurally diverse. The classification based on the cluster analysis indicated that distinct groups did not exist, as there was significant overlap. In general, groups derived from the cluster analysis were similar to those based on the visual assessment. One difference was that in the cluster analysis taro and gatae (Erythrina spp.) dominated sites emerged as a separate group. In addition, the cluster analysis was able to distinguish several subgroups within the mixed crop plantation type. No single socio-economic variable was correlated with vegetative patterns. This suggests that socio-economic variables do not determine vegetation in agroforestry systems and that human preference may be more of a driving factor than initially expected. It is likely that the availability of external resources allows for the selection of species within agroforestry systems to be based on choice rather than need. This trend is likely to increase as people become less dependent upon agroforestry systems to supplement needs. Traditional and institutionalized agroforestry systems have the potential to contribute to increasing self-sufficiency among American Samoan households. Because the importance of these systems is often not realized, the active promotion and education of agroforestry practices is essential. The classification of agroforestry systems provides an organizational framework for future research to build upon. The concept of the ecological complexity continuum where agroforestry systems fall along major points may be useful for answering socio-economic and ecological questions related to local agroforestry production.
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